Much attention has been focused on the use of bacterial species or consortia of species in efforts to remediate contaminated soils or waters from the effects of organic and metal toxicants. Less attention has been paid to plants' ability to sequester and detoxify pollutants, although there is increasing interest in the array of actions that generally are called "phytoremediation." Plants often support associated herbivores that may in fact take up the contaminating compounds directly or chemically modified, and plants also typically are associated with soil fungi that may exert chemical effects on pollutants in the local rhizosphere environment. This project begins to explore these interconnected processes, in a comparative ecological study of saltmarsh cordgrass Spartina alterniflora and the common reed Phragmites australis at field sites in the Hackensack Meadowlands of New Jersey. One major focus is on levels of mercury compounds in soil, water, plant parts, rhizosphere zone, and in associated fiddler crabs and grass shrimp, in an effort to track the fate of mercury compounds present in the area through various potential trophic transfers. In addition, copper, lead, and chromium are also being analyzed, as well as selenium which may affect mercury uptake under some conditions. One main hypothesis under test is whether Spartina takes up more mercury than does Phragmites but more readily releases it through plant detritus or direct excretion on leaf and stem surfaces. Increasing interest in remediation strategies that employ native or introduced plants reinforces the need for basic understanding of the physiological and ecological processes operating among plants. An ecological perspective introduces two classes of process that may affect the availability of metal contaminants to remediation. Direct herbivory may transfer metal toxicants to associated animals in the environment, whether chemicaly modified or not; secondly, fungi and bacteria associated with plant roots in the rhizosphere zone may exert effects on uptake and chemistry of metal compounds into plants. Understanding the interconnections among these processes will benefit future management strategies for remediation of polluted environments.
